Method for the Nondestructive Detection of Cracking in Cast Stainless Steel Components

Cast austenitic stainless steel (CASS) can be found in every light water reactor primary coolant loop system in both boiling water and pressure water nuclear reactors. To date, no effective in-service volumetric nondestructive method exists for the inspection of this material even though some components fabricated from CASS are subject to inspection requirements described in the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel Code, Section XI, Rules for In-service Inspection of Nuclear Power. Conventional ultrasonic inspection techniques have proven to be unreliable on CASS materials. The objective of this investigation is to develop and demonstrate a unique ultrasonic approach for the detection and sizing of surface connected cracking. The proposed technique utilizes a state-of-the-art portable ultrasonic EMAT phased array system designed for the inspection CASS by: 1) eliminating the need to detect low level signals, 2) maximizing energy and spatial resolution at the flaw location through electronic beam focusing, 3) utilizing horizontally polarized shear waves shown to be effective in penetrating through columnar micro-structure and 4) using low frequency sound waves required for maximum material penetration. Commercial Applications and Other Benefits: An immediate market will develop for this technique/hardware in the nuclear industry once demonstrated and passed through an ASME qualification process. This technology is also important for the safe and reliable implementation of future reactor designs by providing a method of inspection for components that are currently un-inspectable.